Biomechanical Responses of Small Female Human Surrogates during Frontal Sled Tests using a Realistic Vehicle Environment

Abstract

There is evidence to suggest that males and females respond differently in motor vehicle collisions, making it important to study how both sexes respond to vehicle safety systems. The THOR 5th-percentile female (THOR-05F) anthropomorphic test device (ATD) was developed to represent a small female occupant better than the Hybrid III 5th percentile female (HIII-05F) ATD. However, the two ATDs have not been compared to post-mortem human surrogate (PMHS) responses using a realistic, driver-seat environment to assess biofidelity or ability to predict injury. Therefore, the objective of this study was to compare the responses of the two ATDs and small female PMHS in matched frontal sled tests simulating a realistic driver-seat environment. A 7th-generation Toyota Camry driver seat test buck was used with Camry parts (i.e., 3-point belt, modified seat, steering wheel, airbag, and column). The belt was equipped with a 4-kN load limiter and a pretensioner. Sixteen tests were conducted with the HIII-05F, THOR-05F, or PMHS using speeds of 30 and 56 kph. A Vicon motion capture system was used to track positions and orientations of the head, T1, T8, L2, and the sacrum. Three-axis accelerometer arrays were also mounted on the head, chest (T8), and the sacrum for all surrogates. The sternum chest potentiometer and Infra-Red Telescoping Rods for the Assessment of Chest Compression (IR-TRACC) were used to measure internal deflections for the HIII-05F and THOR-05F respectively. Chestbands were used to measure external deflections for all surrogates. The THOR-05F matched the PMHS kinematics better than the HIII-05F did. This assessment was made using quantitative comparison of signal peaks and qualitative comparison of signal shapes. Upper neck compression in the HIII-05F was 2900 N greater for the 30-kph tests than the 56-kph. Despite the HIII-05F neck injury criterion (Nij) predicting level 3 neck injury on the Abbreviated Injury Scale (AIS) for the 30-kph tests, no cervical spine fractures occurred in the PMHS tests, suggesting the HIII-05F might over predict neck injury in this loading scenario compared to the THOR-05F. Chest deflections were greater in the THOR-05F tests, which was likely due to the more compliant rib cage. Overall, the PMHS might have deflections more similar to the THOR-05F than the HIII-05F. The HIII-05F might capture the maximum deflection at the upper chest better with the chest potentiometer, while the THOR-05F might better capture the lower chest deflection with an IR-TRACC. AIS 3 thorax injury occurred in the 56-kph PMHS test (4 rib fractures). However, the HIII-05F chest deflection injury risk curve did not predict AIS 3+ level injury. Greater chest deflections in the THOR-05F test might predict thorax injury more accurately. The HIII-05F and THOR-05F had different kinematic, neck, and chest responses. The THOR-05F was similar to the PMHS in more aspects than the HIII-05F was similar (e.g., head excursions, chest deflections). Both ATD responses were more similar to the PMHS for the 56-kph tests compared to the 30-kph tests. More PMHS tests will help reinforce conclusions.